Random access configuration

1. A method comprising: receiving a first cell-defining synchronization signal block on a carrier; synchronizing to the first cell-defining synchronization signal block; receiving a first system information message associated with a first serving cell of the carrier of the first cell-defining synchronization signal block, wherein the first system information message includes a first random access channel configuration; receiving a bandwidth part configuration via a dedicated message from the first serving cell that indicates a bandwidth part configured with a second random access channel configuration different from the first random access channel configuration; and performing random access according to the second random access channel configuration in the bandwidth part of the first serving cell.

2. The method of claim 1 , wherein the second random access channel configuration is associated with a second cell of a second cell-defining synchronization signal block of the carrier.

3. The method of claim 2 , wherein the first cell-defining synchronization signal block is from a first transmission and reception point and the second cell-defining synchronization signal block is from a second transmission and reception point, and the first and second transmission and reception points: are part of the same entity, are connected via a backhaul, are controlled by a common scheduling unit, or some combination thereof.

4. The method of claim 2 , wherein the second cell is not a serving cell.

5. The method of claim 2 , further comprising receiving information corresponding to the second cell-defining synchronization signal block, wherein the information corresponding to the second cell-defining synchronization signal block includes a physical cell identity and a synchronization signal frequency location of the second cell-defining synchronization signal block.

6. The method of claim 2 , further comprising: receiving an indication that indicates that the second cell-defining synchronization signal block is associated with the second random access channel configuration and that the first cell-defining synchronization signal block is not quasi-collocated with the second cell-defining synchronization signal block; determining a downlink timing and a downlink path loss estimate based on the second cell-defining synchronization signal block; and transmitting a random access channel on a random access channel resource corresponding to the second random access channel configuration.

7. The method of claim 1 , wherein the first system information message includes at least a portion of the second random access channel configuration.

8. The method of claim 1 , wherein the first system information message includes system information for a connection set-up but not included in a master information block.

9. The method of claim 1 , wherein the first system information message is received in at least a portion of the carrier on which the first cell-defining synchronization signal block is received.

10. The method of claim 1 , wherein a portion of the carrier on which the first cell-defining synchronization signal block is received comprises a first portion of the carrier and corresponds to a first default downlink bandwidth part of the first serving cell.

11. The method of claim 10 , further comprising receiving an indication reconfiguring the first default downlink bandwidth part to a second default bandwidth part associated with a second portion of the carrier and a non-serving cell-defining synchronization signal block in the second portion of the carrier.

12. The method of claim 11 , wherein the indication indicates to a remote unit to reconfigure the non-serving cell-defining synchronization signal block in the second portion of the carrier as a serving cell-defining synchronization signal block.

13. The method of claim 1 , further comprising receiving a first indication indicating that the second random access channel configuration is associated with a non-serving cell-defining synchronization signal block and allows contention-based random access.

14. The method of claim 13 , further comprising receiving a second indication that indicates whether the non-serving cell-defining synchronization signal block and the first cell-defining synchronization signal block are quasi-collocated.

15. The method of claim 1 , further comprising, in response to not receiving an indication that the second random access channel configuration allows contention-based random access, determining that the second random access channel configuration bars contention-based random access and allows contention free random access on a random access channel resource associated with the second random access channel configuration.

16. The method of claim 1 , wherein the second random access channel configuration is received in a second system information message of the first serving cell, and the second system information message includes system information not essential for a connection set-up.

17. An apparatus comprising: a receiver that receives a first cell-defining synchronization signal block on a carrier; and a processor that synchronizes to the first cell-defining synchronization signal block, wherein: the receiver: receives a first system information message associated with a first serving cell of the carrier of the first cell-defining synchronization signal block, wherein the first system information message includes a first random access channel configuration; and receives a bandwidth part configuration via a dedicated message from the first serving cell that indicates a bandwidth part configured with a second random access channel configuration different from the first random access channel configuration; and the processor performs random access according to the second random access channel configuration in the bandwidth part of the first serving cell.

18. The apparatus of claim 17 , further comprising a transmitter, wherein the second random access channel configuration is associated with a second cell of a second cell-defining synchronization signal block of the carrier, and wherein: the receiver receives an indication that indicates that the second cell-defining synchronization signal block is associated with the second random access channel configuration and that the first cell-defining synchronization signal block is not quasi-collocated with the second cell-defining synchronization signal block; the processor determines a downlink timing and a downlink path loss estimate based on the second cell-defining synchronization signal block; and the transmitter transmits a random access channel on a random access channel resource corresponding to the second random access channel configuration.

19. The apparatus of claim 17 , wherein the first system information message includes at least a portion of the second random access channel configuration.

20. The apparatus of claim 17 , wherein, in response to not receiving an indication that the second random access channel configuration allows contention-based random access, the processor determines that the second random access channel configuration bars contention-based random access and allows contention free random access on a random access channel resource associated with the second random access channel configuration.